+ Fix various formatting.
+ Provide a more detailed walkthrough for dependency injection.
+ Add C# note at intro.

+ Rename Guides.Concepts.Logging title from 'Logging' to 'Logging Events/Data'.
+ Rewrite various sections of Guides.GettingStarted.FirstBot and Guides.GettingStarted.Installing based on suggested changes from #1027.
+ Rename project.csproj example to project.xml to avoid auto-compilation from Visual Studio Code.
+ Rename 'samples\intro' to 'samples\first-bot' to reflect on the article name change.
+ Clean first-bot samples.

This change is because how our repo and project namespace uses .Net instead of .NET.
For consistency sake, we should refer to the project as Discord.Net.